There are two conflicting requirements on the reproduction power used in reproduction of information from an optical disc. From the viewpoint of reproduced signal quality, reproduction with the highest possible power is advantageous because noise is reduced. From the viewpoint of the ability of the optical disc to withstand the reproduction power, however, and the viewpoint of the life span of the semiconductor laser, reproduction with the lowest possible power is advantageous. To meet these conflicting requirements, it is desirable to reproduce at a reproduction power setting that can guarantee a minimum reproduced signal quality while avoiding degradation of the characteristics of the recorded marks on the optical disc and enabling the optical disc to be used as long as possible.
In a conventional optical disc device, when still reproduction is carried out, that is, when the same track is repetitively reproduced, the track suffers much thermal damage and the recorded marks constituting the recorded information in the track degrade, resulting in degradation of reproduced signal quality. An existing remedy to this problem is to detect the amplitude of the reproduced signal during still reproduction and control the reproduction power so as to correct for fluctuations in the amplitude of the reproduced signal (See Patent Document 1, for example).